<template>
    <span>
      {{displayValue}}
    </span>
</template>
<script>
import { requestAnimationFrame, cancelAnimationFrame } from './requestAnimationFrame.js';
export default {
	name : 'CountTo',
	props : {
		startVal : {
			type : Number,
			required : false,
			default : 0
		},
		endVal : {
			type : Number,
			required : false,
			default : 2017
		},
		duration : {
			type : Number,
			required : false,
			default : 3000
		},
		autoplay : {
			type : Boolean,
			required : false,
			default : true
		},
		decimals : {
			type : Number,
			required : false,
			default : 0,
			validator (value) {
				return value >= 0;
			}
		},
		decimal : {
			type : String,
			required : false,
			default : '.'
		},
		separator : {
			type : String,
			required : false,
			default : ','
		},
		prefix : {
			type : String,
			required : false,
			default : ''
		},
		suffix : {
			type : String,
			required : false,
			default : ''
		},
		useEasing : {
			type : Boolean,
			required : false,
			default : true
		},
		easingFn : {
			type : Function,
			default (t, b, c, d) {
				return c * (-Math.pow(2, -10 * t / d) + 1) * 1024 / 1023 + b;
			}
		}
	},
	data () {
		return {
			localStartVal : this.startVal,
			displayValue : this.formatNumber(this.startVal),
			printVal : null,
			paused : false,
			localDuration : this.duration,
			startTime : null,
			timestamp : null,
			remaining : null,
			rAF : null
		};
	},
	computed : {
		countDown () {
			return this.startVal > this.endVal;
		}
	},
	watch : {
		startVal () {
			if (this.autoplay) {
				this.start();
			}
		},
		endVal () {
			if (this.autoplay) {
				this.start();
			}
		}
	},
	mounted () {
		if (this.autoplay) {
			this.start();
		}
		this.$emit('mountedCallback');
	},
	methods : {
		start () {
			this.localStartVal = this.startVal;
			this.startTime = null;
			this.localDuration = this.duration;
			this.paused = false;
			this.rAF = requestAnimationFrame(this.count);
		},
		pauseResume () {
			if (this.paused) {
				this.resume();
				this.paused = false;
			} else {
				this.pause();
				this.paused = true;
			}
		},
		pause () {
			cancelAnimationFrame(this.rAF);
		},
		resume () {
			this.startTime = null;
			this.localDuration = +this.remaining;
			this.localStartVal = +this.printVal;
			requestAnimationFrame(this.count);
		},
		reset () {
			this.startTime = null;
			cancelAnimationFrame(this.rAF);
			this.displayValue = this.formatNumber(this.startVal);
		},
		count (timestamp) {
			if (!this.startTime) this.startTime = timestamp;
			this.timestamp = timestamp;
			const progress = timestamp - this.startTime;
			this.remaining = this.localDuration - progress;

			if (this.useEasing) {
				if (this.countDown) {
					this.printVal = this.localStartVal - this.easingFn(progress, 0, this.localStartVal - this.endVal, this.localDuration);
				} else {
					this.printVal = this.easingFn(progress, this.localStartVal, this.endVal - this.localStartVal, this.localDuration);
				}
			} else {
				if (this.countDown) {
					this.printVal = this.localStartVal - ((this.localStartVal - this.endVal) * (progress / this.localDuration));
				} else {
					this.printVal = this.localStartVal + (this.endVal - this.localStartVal) * (progress / this.localDuration);
				}
			}
			if (this.countDown) {
				this.printVal = this.printVal < this.endVal ? this.endVal : this.printVal;
			} else {
				this.printVal = this.printVal > this.endVal ? this.endVal : this.printVal;
			}

			this.displayValue = this.formatNumber(this.printVal);
			if (progress < this.localDuration) {
				this.rAF = requestAnimationFrame(this.count);
			} else {
				this.$emit('callback');
			}
		},
		isNumber (val) {
			return !isNaN(parseFloat(val));
		},
		formatNumber (num) {
			num = num.toFixed(this.decimals);
			num += '';
			const x = num.split('.');
			let x1 = x[0];
			const x2 = x.length > 1 ? this.decimal + x[1] : '';
			const rgx = /(\d+)(\d{3})/;
			if (this.separator && !this.isNumber(this.separator)) {
				while (rgx.test(x1)) {
					x1 = x1.replace(rgx, '$1' + this.separator + '$2');
				}
			}
			return this.prefix + x1 + x2 + this.suffix;
		}
	},
	destroyed () {
		cancelAnimationFrame(this.rAF);
	}
};
</script>
